It\u2019s a measure of human ingenuity and curiosity that scientists debate the possibility of life on Venus. They established long ago that Venus\u2019 surface is absolutely hostile to life. But didn\u2019t scientists find a biomarker in the planet\u2019s clouds? Could life exist there, never touching the planet\u2019s sweltering surface? <\/p>\n
It seems to depend on who you ask. <\/p>\n
<\/p>\n We\u2019ll start with phosphine. <\/p>\n Phosphine is a biomarker, and in 2020, researchers reported the detection of phosphine in Venus\u2019 atmosphere. There should be no phosphine because phosphorous should be oxidized in the planet\u2019s atmosphere. According to the paper, no abiotic source could explain the quantity found, about 20 ppb. <\/p>\n Subsequently, the detection was challenged. When others tried to find it, they couldn\u2019t. Also, the original paper\u2019s authors informed everyone of an error in their data processing that could\u2019ve affected the conclusions. Those authors examined the issue again and mostly stood by their original detection. <\/p>\n At this point, the phosphine issue seems unsettled. But if it is present in Venus\u2019 atmosphere and is biological in nature, where could it be coming from? Venus\u2019s surface is out of the question. <\/p>\n That leaves Venus\u2019 cloud-filled atmosphere as the only abode of life. While the idea might seem ridiculous at first glance, researchers have dug into the idea and generated some interesting results. <\/p>\n In a new paper, researchers examine the idea of microscopic life that lives and reproduces in water droplets in Venus\u2019s clouds. The title is \u201cNecessary Conditions for Earthly Life Floating in the Venusian Atmosphere.\u201d The lead author is Jennifer Abreu from the Department of Physics and Astronomy, Lehman College, City University of New York. The paper is currently in pre-print. <\/p>\n \u201cIt has long been known that the surface of Venus is too harsh an environment for life,\u201d the authors write. \u201cContrariwise, it has long been speculated that the clouds of Venus offer a favourable habitat for life but regulated to be domiciled at an essentially fixed altitude.\u201d So, if life existed in the clouds, it wouldn\u2019t be spread throughout. Only certain altitudes appear to have what\u2019s needed for life to survive. <\/p>\n The type of life the authors envision aligns with other thinking about Venusian atmospheric life. \u201cThe archetype living thing <being> the spherical hydrogen gasbag isopycnic organism,\u201d they state. (Isopycnic means constant density; the other terms are self-explanatory.)<\/p>\n Here\u2019s how the authors think it could work.<\/p>\n Venus is shrouded in clouds so thick we can only see the surface with radar. The clouds reach all the way around the globe. The cloud base is about 47 km (29 miles) from the surface, where the temperature is about 100 C (212 F.) At equatorial and mid-latitudes, they extend up to a 74 km (46 miles) altitude, and at the poles, they extend up to about 65 km (40 miles.)<\/p>\n The clouds can be subdivided into three layers based on the size of aerosol particles: the upper layer from \u201cIt has long been suspected that the cloud decks of Venus offer an aqueous habitat where microorganisms can grow and flourish,\u201d the authors write. Everything life needs is there: \u201cCarbon dioxide, sulfuric acid compounds, and ultraviolet (UV) light could give microbes food and energy.\u201d<\/p>\n Because of temperature, life in Venus\u2019 clouds would be restricted to a specific altitude range. At 50 km, the temperature is between 60 and 90 degrees Celsius (140 and 194 degrees Fahrenheit). The pressure at that altitude is about 1 Earth atmosphere. <\/p>\n There\u2019s a precedent for life existing in the clouds. It happens here on Earth, where scientists have observed bacteria, pollen, and even algae at altitudes as high as 15 km (9.3 miles.) There\u2019s even evidence of bacteria growing in droplets in a super-cooled cloud high in the Alps. The understanding is that these organisms were carried aloft by wind, evaporation, eruptions, or even meteor impacts. But there\u2019s an important difference between Earth\u2019s and Venus\u2019 clouds.<\/p>\n Earth\u2019s clouds are transient. They form and dissolve constantly. But Venus\u2019 clouds are long-lasting. They\u2019re a stable environment compared to Earth\u2019s clouds. In Earth\u2019s clouds, aerosol particles are sustained for only a few days, while in Venus\u2019 clouds, the particles can be sustained for much longer periods of time.<\/p>\n Add it all up, and you get stable cloud environments where aerosol particles can sustain themselves in an environment where energy and nutrients are available. The researchers say that though eventually aerosol particles and the life within them will fall to the surface, they have time to reproduce before that happens.<\/p>\n The idea of a microbial life cycle in Venusian clouds was developed by other researchers in their 2021 paper \u201cThe Venusian Lower Atmosphere Haze as a Depot for Desiccated Microbial Life: A Proposed Life Cycle for Persistence of the Venusian Aerial Biosphere.\u201d <\/p>\n There are five steps in Venus\u2019s proposed cloud lifecycle:<\/p>\n In this new work, the researchers focus on time. <\/p>\n \u201cOne of the key assumptions of the aerial life cycle put forward in Seager et al. 2021 is the timescale on which droplets would persist in the habitable layer to empower replication,\u201d the authors write. \u201cIt is this that we now turn to study.\u201d<\/p>\n The authors used E. Coli generation times under optimal conditions in their work. In aerobic and nutrient-rich conditions, E. Coli can reproduce in 20 minutes. So, the E. Coli population will double three times in one hour. Bacteria must reproduce faster than they fall to the surface to sustain itself. They need to form a colony.<\/p>\n The researchers calculated that to sustain itself, the time it takes for bacteria to fall from the habitable part of the atmosphere to the inhabitable has to be longer than half an Earth day. As droplet size increases, the droplets would begin to sink. \u201cAs the droplet size approaches 100 \u00b5m, the droplets would start sinking to the lower haze layers,\u201d they explain. However, their detailed calculations show that reproduction outpaces the fallout rate. <\/p>\n According to the team\u2019s work, a population of bacteria could sustain itself in Venus\u2019 clouds.<\/p>\n There are, obviously, still some questions. How certain are we that nutrients are available? Is there enough energy? Are there updrafts that can loft spores into the right layer of the atmosphere?<\/p>\n But the real big question is how was this all set in motion? <\/p>\n \u201cAn optimist might even imagine that the microbial life actually arose in a good-natured surface habitat, perhaps in a primitive ocean, before the planet suffered a runaway greenhouse, and the microbes lofted into the clouds,\u201d the authors write. If that\u2019s the case, this unique situation arose billions of years ago. Is there any other possibility? Could life have originated in the clouds? <\/p>\n Much scientific investigation into Venus, phosphine, clouds, and life relies on scant evidence. Few are willing to go out on a limb and proclaim that Venus can and does support life. We need more evidence. <\/p>\n For that, we have to wait for missions like the Venus Life Finder Mission. It\u2019s a private mission being developed by Rocket Lab and a team from MIT. Who knows what VLF and other missions like DAVINCI and VERITAS will find? Stronger evidence of phosphine? Better data on Venus\u2019 atmospheric layers and the conditions in them? <\/p>\n Life itself? <\/p>\n![\"Cloud](\"https:\/\/www.universetoday.com\/wp-content\/uploads\/2021\/10\/Venus_-_December_23_2016.jpg\")
56.5 to 70 km altitude, the middle layer from 50.5 to 56.5 km, and the lower layer from 47.5 to 50.5 km. The smallest droplets can float in all three layers. But the largest droplets, which the authors call type 3 droplets with a radius of 4 \u00b5m, are only present in the middle and lower layers. <\/p>\n![\"This](\"https:\/\/www.universetoday.com\/wp-content\/uploads\/2024\/04\/Venus-Cloud-Life-1.jpg\")
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